This disclosure relates to the formation of patterns for semiconductor devices, in particular, to the formation of patterns for thin film transistors (TFT).
Current TFT processes use 5 masks. Such masks may be use to form patterns through photolithography. During photolithography, a photosensitive material is deposited on a layer to be patterned. A mask is used to expose the photosensitive material. The exposed photosensitive material is removed during a developing process. The remaining photosensitive material is used as an etch mask to pattern the layer to be patterned. After patterning, the remaining photosensitive material is removed. Such processes are performed for each mask used in forming the TFT.
In forming a TFT, both a semiconductor layer for the channel of the TFT and a conductive layer for the source and drain contacts are patterned. Typically, separate masks are used for each layer. Thus, as described above, two photolithography process are used to form the etch masks. 
As the number of masks and corresponding photolithography steps increase, manufacturing time and costs similarly increase. Thus, there remains a need for an improved technique for forming patterns.